Dataset: lobster tag_size and condition

Mapping Spawning and Hatching Grounds of the American Lobster
Tagging Data

Project Leader: Diane Cowan, The Lobster Conservancy

Additional Participants: Mathew Thomson, F/V Shearwater
Win Watson, University of New Hampshire
Matthew Weber
Andrew Solow, Woods Hole Oceanographic Institution
Mark Wallace, F/V Pamela B
Tim Thompson, F/V Haley & Amy
Bill Rourke, F/V A-Bill
Michael Reny
Richard Nelson, F/V Pescadero
Peter Murphy
Jon Murphy, F/V Redeemed
Steve Lash, F/V Streaker II
Troy Hayes, F/V Gray Ghost
Mark Havener, F/V Sarah Ashley
Philip Genthner, F/V Melinda Kay
Darrell Brazier, F/V Amy Sue
Nick Caloyianis, Caloyianis Productions, Inc.
Clarita Berger, Caloyianis Productions, Inc.
Richard Barter, F/V Tammy Jeane II
Kevin Benner, F/V Wanda Marie
Rex Benner, F/V Sydni & Erik
Denny Benner, F/V Maureen R
Jim Bolen, F/V Finest Kind
Philip Bramhall, F/V Amanda Kate

The Lobster Sonar Tracking Project was launched in late summer 2002, and was implemented for 2 tracking seasons. In September and October of the first season (2002) a total of 191 egg-bearing females were tagged: lobster IDs: 001 - 193. These lobsters were then tracked over the subsequent 13 months. In August and September of 2004 - the second season of the project - 45 egg-bearing females AND 41 males were tagged, a total of 86 lobsters: lobster IDs: 300 - 400.

Each lobster was tagged with three pieces of equipment: a sonar transmitter that emits a unique frequency/code combination, a temperature datalogger ("Tidbit") that records the ambient water temperature every hour, and a ribbon tag with the lobster's ID and The Lobster Conservancy (TLC) phone number to identify the lobster in the event of recapture. Participants were equipped with vessel-based hydrophones to periodically "listen" for sonar signals throughout their fishing territory. Frequency and code were recorded from each observed signal and the lobster ID was subsequently looked up. Hence, the tagged lobsters could be tracked any one of three ways: via hydrophone, trap recapture, or SCUBA dive recapture (using an underwater dive receiver). Information on lobster egg state could only be collected upon recapture. Likewise, temperature data collected by the Tidbit was only useful if the logger was recovered upon recapture and the information downloaded. Temperature data on 30 lobsters from the 2002-2003 season and 18 lobsters from the 2003-2004 season were downloaded as well as data from stationery loggers. Each lobster ID in that data object corresponds to lobster IDs in the associated data objects.

Project website: http://www.lobsters.org

Associated data: water temperature, lobster tracking data and lobster recapture data

Lobster Tag Data:
South missing
4=dbl crusher
5=dbl seizer 0 if lobster is missing no appendages;
If appendages are missing (other than antennae), this is the number of missing claws,
plus legs, plus maxillipeds, plus uropods.
(see 'comments' for which appendages are missing) 4= hatching explanation of the use of this code)

Validity code:
There is obviously room for human error in the collection of these data, and potential equipment errors as well. Incorrect sonar codes can be recorded, data can be incorrectly entered into the database, and sonar tags can and have fallen off lobsters without the investigators' knowledge (they will continue beeping away on the ocean floor). Therefore, the most confident tracking data was collected on a lobster that was subsequently recaptured (with the sonar tag still visibly attached). Slightly less confidence was awarded to tracking data on a lobster that showed movement, but has not been subsequently recaptured to verify sonar tag presence. Least confidence and most suspicion exists for tracking data that indicates a sonar tag has not moved for some time, and the lobster has not been subsequently recaptured. This indicates a good possibility that the tag has fallen off. Furthermore, through spatial analysis of most of the individual lobster tracks in GIS mapping software, a number of specific data points were noted that were either highly suspicious or downright impossibilities.

If a recapture showed that the sonar tag was missing, then every prior tracking record for that lobster received a "transmitter detached" reflecting uncertainty as to when the tag was lost. "Disappeared" means the lobster was never tracked or recaptured. Based upon spatial analysis we were able to determine that some of the tracking entries were "invalid", while others were "suspect". These validity descriptions are complete for every lobster tracked during the first year of the project, but not yet complete for the second year.

Revised Sept 05, 2006; gfh